What should i do so i can date the girl i like?

Life is starting to get complicated. Really complicated. I am currently in a relationship, though I'm mostly like going to dump her because we have became more like friends. She goes to a different school and i no longer like her. However at the school i go to i think their is a girl who likes me, but i can't be certain. I caught her looking at me sometimes, however she caught me once or twice as well. If you didn't know already I sorta like her too. This might be clouding my judgement which is why I need an outside opinion. She is usually the first one to say hi in the hallways. One time the ball got stuck on top of the bleachers. I'm on my athletic side so i just got up and got it. Just about when I was about to jump off, she told me not to because she didn't want to see me getting hurt, so i did more of a half jump. She still cupped her eyes as i jumped. We only talk in school and that's all, but I'm still curious to hear everyone's opinion. Oh and please no comments on how this is unfair to my current girlfriend. The heart feels what it feels and I don't plan on cheating her. We are all sopres. However i dont talk to the girl i like often. Its more of in a sequence of burst. How should i find out for sure that she likes me? and then how to ask her out. I am on the shy side when it comes to dating. I just want some tips and some answers to my questions.